1. Field of the Invention
The invention relates to a system for navigating a free ranging vehicle which is provided with steering and control means, the system comprising means for detecting the position of the vehicle on the surface on which the vehicle moves and means for determining and/or correcting the path to be followed by the vehicle between an arbitrary starting point and an arbitrary destination.
2. The Prior Art
The problems relating to navigation of a free ranging vehicle are described in the article, "Free Range AGV Uses Laser Guidance", published in FMS Magazine, July 1983. However, the solution given in this article, i.e., the use of a number of coded beacons which are scanned by a laser beam is not without problems: the processing of the various signals is very complicated, an acceptable accuracy is difficult to obtain, and it is clear that this system can only be used on surfaces on which there are no high obstructions.
British Patent Specification No. 1,150,029 describes a system for guiding a vehicle provided with its own driving motor, based upon the use of an active network of electrical conductors carrying an alternating current, the vehicle following the path of the wires by sensing the electromagnetic field around the conductor. The vehicle to be guided starts by following a certain conductor and counts the number of transverse conductors which has been passed by it; after a predetermined number of these conductors have been passed, a left- or right hand turn can be initiated, and so on.
The number of starting points and destinations and the path to be followed are thus limited; the necessity to bury the insulated conductors (which necessarily may not be interrupted) in the ground, makes this known system in face only suitable for agricultural applications, such as described in the noted patent speicification, where the above-mentioned disadvantages can be tolerated.
The present invention aims to provide a navigation system by means of which a vehicle can be navigated with an accuracy which is sufficient for practical purposes, which does not require extensive modifications of the surface on which the vehicles runs and which is in its operation so flexible that practically any surface can be adapted to be used with the system according to the invention, and with which navigation can be effected between any arbitrary starting point and destination. In this connection it should be noted that the term navigation is meant the process of determining a suitable path for travel between a known starting position and an arbitrary destination, and the process of verification and correction of the path that is actually followed towards the planned path.